The invention concerns a sports-shoe sole with metal bushes open toward the sole tread surface and comprising fastening elements at its inner wall to mount grippers such as studs, spikes, golf cleats etc.
Sports-shoe soles of the above kind fitted with threaded steel or aluminum insets have long been widely known. The associated grippers such as studs or spikes comprise threaded steel pins. If the shoes are golf shoes, the threaded metal insets comprise inside threads of 0.283 2' and the associated cleats matching outer threads. As regards other sports shoes, size M5 inner or outer threads are typical. The advantages of this known fastening system consist, on one hand, of world-wide acceptance (they represent virtually the professional standard) and, on the other hand, of the simple and low manufacturing costs of soles with inserted or subsequently forced-in threaded insets.
However the state of the art also entails substantial drawbacks. Illustratively steel insets, even though plated as a rule, tend to rust, and aluminum threads are susceptible to damage. While the threaded pins of the studs/spikes cooperating with the threaded insets in the sole are also plated, they will also rust if damaged even slightly, and then may be stuck due this rusting in the threaded insets.
Especially as regards the sportsmen, it is also drawback that the known connection system is fairly heavy on account of the metal parts being used. This comparatively high weight of the known connection system also arises in that the threaded metal insets can only be installed in solid plastics with relatively high rigidity in order to be reliably anchored in the sole. If on the other hand such threaded metal insets are anchored in rubber or plastic foam soles, their anchoring area must be made appropriately large and their edges must be rounded to prevent notching and cutting. As a result the threaded insets will be big, heavy and expensive.
If the grippers proper are made conventionally from a lightweight material, for instance from plastic, rubber, leather or aluminum, then the gripper will be in two parts because the threaded pin cooperating with the threaded inset in the sole as a rule is required to consist of steel (anchoring requirement), but this dual-part feature represents costly manufacture. (Threaded pins made of aluminum are the exception).
Another inadequacy feature of the known connection system is that moisture can pass through the threads into the shoe.
Moreover it is known to affix plastic insert parts in plastic shoe soles, said insert parts evincing an inner thread width of 10 mm. The associated grippers such as soccer studs or golf spikes comprise plastic bases with a matching outer thread. Because of the absence of metal parts, the known connection system is characterized by low weight. Nor are there any rust-susceptible parts, and there is no danger of the grippers freezing into place in the sole by rusting. Again the grippers can be manufactured in simple manner as integral injection-molded parts.
Nevertheless this known connection system also incurs various drawbacks and insufficiencies. The threads of the sole insets on one hand and on the other hand the gripper pins are fairly easily damaged by foreign bodies (pebbles, soil), especially when changing the grippers. The comparative softness of the plastic easily allows undesired loosening of the thread connection. While special measures are taken in some embodiments to prevent such loosening (for instance serrations), such measures perforce entail higher complexity and costs in manufacture. Replacing damaged or worn grippers frequently is possible only with difficulty because the connecting system being discussed deviates from the professional standard.